Splatoon seems like something perfect for the F2P model, fairly generic characters with an interesting co-op shooter concept. If they had a good enough install base of the Wii U, I think it'd be the perfect opportunity for them to push-install the game to your Wii U to entice you, and offer alternate character models, costumes, other cosmetic changes to the game as micro transactions. I hope I hear differently after launch, but current info on it makes it difficult to see how much value I'd get out of the game. I'd be much more likely to buy it if there was an easy way to try it out first to see if the game is better than I expect.
Wii U is beyond "saving" at this point. Nintendo has produced some of their best games in a while on the Wii U, and that hasn't caught them up to the competition. Nintendo's in a strange position. The Wii was hugely successful because it deviated from the competition and sparked people's interest in motion control with a very successful proof of concept (Wii Sports). Wii U tried to be different by the gamepad, but by the time it released, tablets & touchscreen smart phones are ubiquitous, so while Nintendo may have seen it as a way to extend the success of their DS line of handhelds, I think many others saw it as "oh, they're aping off the success of iPad games.
If they're going to continue their trend of deviation from the competition, they need to create a value proposition to all gamers, not just Nintendo enthusiasts. I think Wii U shows us how Nintendo's systems do now with just core Nintendo fans buying-in, which is probably a very concerning thing to Nintendo. And that's the challenge I don't have an answer to, otherwise I'd be approaching Nintendo looking for a job.